The present invention relates to a rotary piston compressor with horizontal crankshaft, and more specifically to an improvement on its muffler chamber.
The discharge muffler chamber of rotary compressors is usually made up of a certain number of volumes arranged in series and/or parallel, where the pulsations of the discharge gas flow are muffled.
In the discharge through the compressor discharge valve, gas is discharged together with some oil quantity as is typical of rotary compressors. This oil, mostly due to its greater density and viscosity, does not follow the gas flow through the muffler chamber volumes, and ends up by being contained in the chamber till a certain stable level is reached. This can cause several disfunctions, which are:
1--Alteration of the muffler chamber effective volumes and, therefore, alternation of its attenuation characteristic.
2--Since the discharge valve orifice is at a high temperature, as well as the whole muffler chamber, any delay of the passage of oil from these points will increase the its temperature. This has a negative effect upon the compressor efficiency.
Therefore, the oil accumulation and its prolonged contact with the muffler chamber must be avoided in order to keep the oil temperature from increasing.
3--The impact and cavitation noise of the discharge valve reed is obliged to work covered by oil and its efficiency is decreased.
A known arrangement for reducing the oil quantity retained in the interior of the muffler chamber of a horizontal crankshaft rotary compressor is that one proposed by U.S. Pat. No. 4,636,154. In this arrangement, the oil is purged by means of a hole at the center of the muffler chamber, and is conducted up to this hole through channels which direct the discharge flow from its first volume. In spite of contributing for the process of purging the oil, the solution described on U.S. Pat. No. 4,636,154 has the following inconveniences:
The course of the oil flow from the outlet of the first volume of the muffler chamber is not effective enough to avoid oil accumulation at the lowest level of the first volume; the said first level is very near and can be in contact with the discharge valve orifice, thereby causing all problems related to oil heating and noise previously described;
The hole at the center of the muffler chamber for oil discharge may alter the characteristic of its noise attenuation.